1. Field of the Invention
The present invention relates to a device for processing road data or intersection data and, more specifically, to a navigation device in which a route along which a moving body will travel is identified based upon map data, and the route that is identified is displayed to the operator. In particular, the invention relates to a navigation system which learns the route of travel.
2. Description of the Related Art
A conventional navigation device has been disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 194473/1986. According to this navigation device, a map of a desired area is displayed on a display unit based upon the stored map data. Conditions for identifying the facilities are shown on the screen of the display unit, the conditions for identification are selected step by step, and a facility desired by the user is set as a destination.
The position of the thus set facility is indicated by a discrimination mark on the map screen. Based on the map data, furthermore, the navigation device searches a route from the present position to the facility that is set and displays the route on the screen. While the moving body is traveling along the route, the user is informed of various necessary data (road into which the moving body should enter, etc.) by voice or the like means.
The route that is identified is, for example, the one along which the moving body can arrive at the destination traveling a distance which is as short as possible, the one composed of roads which are relatively wide, or the one along which the moving body needs turn to the right or to the left the least number of times. However, the route that is identified does not necessarily include the roads along which the driver usually travels or the roads which the driver prefers.
Moreover, the road data in the map data is stored in a nonvolatile data storage unit, and the roads that are not stored in the nonvolatile data storage unit are not included in the route that is identified. In practice, however, new roads are constructed one after another, and the most desirable route is often not identified by the road data stored in the nonvolatile data storage unit. For example, a route which utilizes the new road may often enable the moving body to move to a desired destination more quickly and more favorably. Changes of the roads result from an increase or a decrease in the number of lanes of the existing roads, the existing road that is constructed as an elevated road, as an underpass or as a solid crossing, construction of a bridge, tunnel and signals.
In particular areas such as the vicinity of the dwelling of the driver, furthermore, it is desired that the roads preferred by the driver are preferentially used as a guide route. In foreign areas, however, it is desirable that wider roads be used as a guide route. In other words, the driver may feel more comfortable in driving when the roads used as a guide route are changed depending upon the area.
In particular, it will become more convenient if data for the roads used for driving the vehicle is saved, and thus the saved road data is utilized for searching a route. Besides, an optimum route can be identified if predetermined amounts of the stored road data can be rearranged.